1.
The sum of the interior angles of a triangle is :
Correct Answer
C. 180
Explanation
The sum of the interior angles of a triangle is always 180 degrees. This is a well-known property of triangles in geometry. It can be proven by dividing a triangle into two right triangles and using the fact that the sum of the angles in a straight line is 180 degrees. Therefore, the correct answer is 180.
2.
If X=5 , Y=6, then : XY(X^2 -Y) = X times Y times (X squared minus Y)
Correct Answer
B. 570
3.
If a specified value is 120.00 , and the measured value is 124.56, the % error is:
Correct Answer
D. 3.8%
Explanation
The percent error is calculated by taking the absolute difference between the measured value and the specified value, dividing it by the specified value, and then multiplying by 100. In this case, the absolute difference between the measured value of 124.56 and the specified value of 120.00 is 4.56. Dividing 4.56 by 120.00 gives 0.038, and multiplying by 100 gives 3.8%. Therefore, the correct answer is 3.8%.
4.
One giga unit is equal to:
Correct Answer
E. 1,000,000,000
Explanation
One giga unit is equal to 1,000,000,000.
5.
Which formula is correct if : A=100, B= 200, and C= 300
Correct Answer
D. B=C-A
Explanation
The formula B=C-A is correct because it subtracts the value of A from C, resulting in the value of B. Given that A=100, B=200, and C=300, substituting these values into the formula gives B=300-100=200, which matches the given value of B.
6.
Kilo equals :
Correct Answer
A. Mega / 1000
Explanation
The correct answer is "mega / 1000" because the prefix "kilo" represents a factor of 1000. Therefore, when converting from "mega" to "kilo", we divide by 1000 to get the equivalent value.
7.
If 4000 was the specified value, and 3850 was the mesured value, what is the percent error?
Correct Answer
B. -3.75
Explanation
The percent error is calculated by taking the absolute difference between the specified value and the measured value, dividing it by the specified value, and then multiplying by 100. In this case, the absolute difference between 4000 and 3850 is 150. Dividing 150 by 4000 gives 0.0375. Multiplying 0.0375 by 100 gives 3.75. However, since the measured value is less than the specified value, the percent error is negative. Therefore, the correct answer is -3.75.
8.
Insulation resistance tests sets usually include ___ test connection terminals.
Correct Answer
C. 3
Explanation
Insulation resistance test sets usually include 3 test connection terminals.
9.
With insulation resistance test equipment :
Correct Answer
A. Leakage current returned by the guard lead are not normally metered
Explanation
The correct answer is "leakage current returned by the guard lead are not normally metered." This means that when using insulation resistance test equipment, the leakage current that is returned by the guard lead is not typically measured or recorded. The guard lead serves the purpose of preventing any leakage current from affecting the accuracy of the measurement being taken. Therefore, it is not necessary to meter or monitor the leakage current returned by the guard lead.
10.
Properly adjusting to the null point of a transformer turns ratio test set :
Correct Answer
C. Is accomplished by changing the adjustable ratio of the test set's reference transformer
Explanation
Adjusting to the null point of a transformer turns ratio test set is accomplished by changing the adjustable ratio of the test set's reference transformer. This means that the ratio of the reference transformer is adjusted until the test set impedance matches the specimen transformer's impedance. This ensures that the test current flow and test voltage are correct during the test.
11.
Typical ground resistance test sets provide :
Correct Answer
D. 4 output terminals
Explanation
Typical ground resistance test sets provide 4 output terminals. These terminals allow for the measurement of ground resistance by connecting the test set to the grounding system. The 4 output terminals provide a means to measure the voltage drop across the ground resistance and the current flowing through it. This allows for accurate testing and evaluation of the ground resistance, ensuring that it meets the required standards for safety and functionality.
12.
An insulation resistance test set has 3 scales on its meter face. The top scale is 3 to 3k gigohms. The center scale is 30 to 30k megohms. The bottom scale is 3 to 30k kilohms. After selecting the center scale and connecting the leads to a 2300 volt , 500 HP motor, the instrument indicates the lowest reading. You have determined that :
Correct Answer
E. B and D are correct
Explanation
Based on the information provided, selecting the center scale and connecting the leads to the motor results in the instrument indicating the lowest reading. This suggests that there are shorted turns in the windings or the motor insulation is weak, both of which can cause a decrease in insulation resistance. Additionally, the fact that the test set is on the wrong scale implies that the value measured should be reported. Therefore, both options B and D are correct.
13.
What is indicated when the turns ratio test set is hard to crank and the correct exciting voltage cannot be reached ?
Correct Answer
E. A or B
Explanation
When the turns ratio test set is hard to crank and the correct exciting voltage cannot be reached, it indicates either incorrect polarity or shorted specimen windings.
14.
Low resistance ohmmeters typically include ____ test connection terminals
Correct Answer
C. 4
Explanation
Low resistance ohmmeters typically include 4 test connection terminals. These terminals are used to connect the ohmmeter to the circuit or device being tested. The additional terminals allow for more accurate measurements by compensating for any resistance in the test leads or connections. Having multiple terminals also provides flexibility in testing different types of circuits or components.
15.
Winding resistance measurements are performed by using a :
Correct Answer
C. Low resistance ohmmeter
Explanation
A low resistance ohmmeter is used for winding resistance measurements because it is specifically designed to measure low resistances accurately. This type of ohmmeter has a very low internal resistance, allowing it to accurately measure the resistance of the winding without affecting the measurement. Megohmeters, on the other hand, are used to measure high resistances, while multimeters are more versatile and can measure a wide range of resistances but may not provide the accuracy required for low resistance measurements. Insulation resistance test sets are used to measure the resistance of insulation materials, not the winding resistance.
16.
Measuring instruments with graduated scales and pointers are referred to as __________ type instruments
Correct Answer
A. Analog
Explanation
Analog instruments are referred to as measuring instruments with graduated scales and pointers. These instruments provide continuous and proportional readings based on the position of the pointer on the scale, allowing for precise measurements. In contrast, digital instruments provide discrete numerical readings, while LED instruments use light-emitting diodes for display. Averaging instruments calculate the average of multiple measurements, and recording instruments continuously record measurements over time. Therefore, the correct answer is analog.
17.
Generally, high current test sets:
Correct Answer
E. Provide high test currents at 10 volts or less
Explanation
High current test sets are designed to provide high test currents at 10 volts or less. This means that they are capable of generating a significant amount of current while maintaining a low voltage level. This is important for testing purposes as it allows for accurate measurements and evaluations of electrical equipment and systems. By providing high test currents at a low voltage, these test sets ensure the safety of the testing process and prevent any potential damage to the equipment being tested.
18.
Which instrument or test set is LEAST likely to be used during the testing of medium voltage cables
Correct Answer
E. Turns ratio test set
Explanation
A turns ratio test set is used to measure the turns ratio of transformers, which is not relevant to the testing of medium voltage cables. The other instruments mentioned, such as the megohmmeter, ohmmeter, DC high potential test set, and voltage detector, are commonly used for testing the insulation resistance, continuity, dielectric strength, and presence of voltage in cables. Therefore, the turns ratio test set is the least likely to be used during the testing of medium voltage cables.
19.
A polorization index test typically requires the use of :
Correct Answer
B. Megohhmeter
Explanation
A polarization index test is a test used to measure the insulation resistance of electrical equipment. It is used to determine the condition of the insulation and detect any potential issues. A megohmmeter, also known as an insulation resistance tester, is the most suitable instrument for this test. It is designed to measure high resistance values, typically in the range of megaohms, which is necessary for accurately assessing the insulation resistance. Therefore, a megohmmeter is required for conducting a polarization index test.
20.
Insulation power factor test equipment
Correct Answer
C. Is frequently used to test transformers
Explanation
The given answer states that insulation power factor test equipment is frequently used to test transformers. This means that this equipment is commonly utilized in the testing process of transformers. It is important to test transformers to ensure their proper functioning and to identify any issues or faults. The insulation power factor test helps in determining the condition of the insulation system of the transformer, which is crucial for its performance and safety. Therefore, the frequent usage of this equipment in testing transformers is justified.
21.
What test equipment is used to test the RTD inputs of a motor protective relay?
Correct Answer
A. Decade box
Explanation
A decade box is used to test the RTD inputs of a motor protective relay. A decade box is a type of test equipment that allows the user to manually set or adjust the resistance value in increments of 1 ohm. This is useful for simulating different resistance values that the RTD inputs may encounter in real-world scenarios. By connecting the decade box to the RTD inputs of the motor protective relay, technicians can verify if the relay responds correctly to the simulated resistance values, ensuring its proper functioning.
22.
Multi-meters can be routinely used to
Correct Answer
E. None of the above
Explanation
The correct answer is "none of the above" because multi-meters are not typically used to measure resistance between switchgear and building neutrals and ground conductors during maintenance testing of ground faults, to prove the integrity of bolted bus and cable connections, or to measure phase angle. Multi-meters are commonly used to measure voltage, current, and resistance in electrical circuits, but the given options do not align with the usual applications of multi-meters.
23.
How would you use a VOM rated at 10 amperes maximum to measure a 100 amp load?
Correct Answer
E. Use a current transformer
Explanation
To measure a 100 amp load using a VOM rated at 10 amperes maximum, a current transformer can be used. A current transformer is a device that steps down the current to a level that can be measured by the VOM. By passing the load's current through the current transformer, the output current can be within the range of the VOM, allowing for accurate measurement.
24.
To measure circuit resistance, first
Correct Answer
B. Check for the presence of voltage
Explanation
To measure circuit resistance, it is important to check for the presence of voltage. This is because if there is voltage present in the circuit, it can affect the accuracy of the resistance measurement. By checking for voltage, we ensure that the circuit is not energized and it is safe to proceed with the resistance measurement.
25.
The maximum voltage rating of a multi-meter used without a high voltage probe is typically
Correct Answer
C. 750-1000 volts RMS, non-continuous
Explanation
A multi-meter is a device used to measure voltage, among other electrical quantities. Without a high voltage probe, the maximum voltage rating of a multi-meter is typically 750-1000 volts RMS, non-continuous. This means that the multi-meter can measure voltages up to this range, but it should not be used continuously at these high voltages as it may damage the device. Therefore, it is important to use a high voltage probe when measuring voltages above this range to ensure accurate readings and to protect the multi-meter from potential damage.
26.
To make a resistance measurement, start with the ohmmeter set on :
Correct Answer
C. The highest resistance scale
Explanation
When making a resistance measurement, it is recommended to start with the highest resistance scale on the ohmmeter. This is because starting with the highest scale allows for a more accurate measurement. If the resistance being measured is too low for the highest scale, then the ohmmeter can be adjusted to a lower scale to get a more precise reading. Starting with the highest resistance scale ensures that the measurement is not affected by any potential errors or limitations of the lower scales.
27.
The batteries in a typical analog multimeter are required for:
Correct Answer
D. Resistance measurements
Explanation
The batteries in a typical analog multimeter are required for resistance measurements because when measuring resistance, the multimeter sends a small current through the circuit being measured and measures the voltage drop across the component. This current is generated by the batteries in the multimeter. Without the batteries, the multimeter would not be able to generate the necessary current to measure resistance accurately. The batteries are not needed for other measurements such as dc voltage, ac voltage, or ampere measurements as those measurements do not require the generation of a current.
28.
Voltage in an electrical system:
Correct Answer
C. Is equivelent to the pressure of a water system
Explanation
Voltage in an electrical system is equivalent to the pressure of a water system. Just like water flows from an area of high pressure to low pressure, electrical current flows from an area of high voltage to low voltage. Voltage can be seen as the force that pushes the electrical current through the system, similar to how pressure pushes water through pipes. Therefore, the analogy of voltage being equivalent to the pressure in a water system helps in understanding the concept of electrical voltage.
29.
On a 575 Delta system, what is the line to line voltage?
Correct Answer
E. 575
Explanation
In a 575 Delta system, the line to line voltage is 575 volts. The term "Delta" refers to the configuration of the electrical connections in the system, where the three phases are connected in a triangular shape. The line to line voltage is the voltage measured between any two of the three phases. In this case, the line to line voltage is equal to the system voltage, which is 575 volts.
30.
Watt is a unit of:
Correct Answer
E. A and D
Explanation
The correct answer is A and D because watt is a unit of both true power and real power. True power refers to the actual power consumed or produced in a circuit, while real power refers to the power that is converted into useful work. Both true power and real power are measured in watts, making options A and D the correct choices.
31.
Capacitance is measured in:
Correct Answer
C. Farads
Explanation
Capacitance is a measure of an object's ability to store electrical charge. It is determined by the ratio of the amount of charge stored on the object to the potential difference across it. The unit of capacitance is the farad, which is equal to one coulomb per volt. Therefore, the correct answer is farads.
32.
There are _____ degrees in one cycle of a sine wave.
Correct Answer
B. 360
Explanation
A sine wave completes one full cycle in 360 degrees. This means that it starts at 0 degrees, reaches its peak at 90 degrees, returns to 0 degrees at 180 degrees, reaches its lowest point at 270 degrees, and completes the cycle at 360 degrees. Therefore, the correct answer is 360.
33.
Reactive power is measured in:
Correct Answer
B. Vars
Explanation
Reactive power is measured in vars, which stands for volt-amp reactive. Reactive power represents the power that oscillates between the source and the load in an alternating current (AC) circuit, without being converted into useful work. It is necessary for the proper functioning of inductive and capacitive loads, such as motors and transformers. While watts represent the real power in an AC circuit, vars specifically measure the reactive component. Voltamps and ohms are units of electrical power and resistance, respectively, but they do not specifically measure reactive power. Joules, on the other hand, measure energy, not power.
34.
An ampere is
Correct Answer
D. One coulomb per second
Explanation
An ampere is defined as one coulomb per second. This means that it represents the rate at which electric charge flows in a circuit. It is a unit of electric current, indicating the amount of charge passing through a point in a circuit per unit of time. The correct answer accurately describes the relationship between an ampere and the flow of electric charge.
35.
The henry is a unit of measurement of
Correct Answer
E. Inductance
Explanation
The henry is a unit of measurement for inductance. Inductance is a property of an electrical circuit that opposes any changes in the current flowing through it. It is caused by the presence of an inductor, which is a passive electronic component that stores energy in a magnetic field when current flows through it. The henry is used to quantify the amount of inductance in a circuit, with larger values indicating higher levels of inductance.
36.
Power factor is calculated by:
Correct Answer
B. KW/kVA
Explanation
The power factor is calculated by dividing the real power (kW) by the apparent power (kVA). This ratio gives an indication of how effectively the electrical power is being used. A higher power factor indicates a more efficient use of power, while a lower power factor indicates a less efficient use. Therefore, kW/kVA is the correct answer for calculating the power factor.
37.
If an AC voltage has a frequency of 350 hertz, how many times will the positive peak value of voltage occur after 2 seconds?
Correct Answer
B. 700
Explanation
The frequency of an AC voltage represents the number of complete cycles it goes through in one second. In this case, the AC voltage has a frequency of 350 hertz, which means it completes 350 cycles in one second. Therefore, in 2 seconds, it will complete 2 times the frequency, which is 700 cycles. Since the positive peak value of voltage occurs once in each cycle, it will occur 700 times in 2 seconds.
38.
What is the turns ratio of a 3 phase 500kVA, 13,200-480 volt rated D-D transformer that is 80% loaded?
Correct Answer
B. 27.5
Explanation
The turns ratio of a transformer is the ratio of the number of turns in the primary winding to the number of turns in the secondary winding. In this question, the transformer is rated 500kVA, which means it can handle a maximum power of 500kVA. Since it is 80% loaded, it is operating at 80% of its maximum power, which is 400kVA. The formula to calculate the turns ratio is (Vp/Vs) = âˆš(Pp/Ps), where Vp and Vs are the primary and secondary voltages, and Pp and Ps are the primary and secondary powers. Plugging in the values given in the question, we get (13200/480) = âˆš(500/400). Solving this equation gives us a turns ratio of 27.5.
39.
What side of the power triangle is the longest?
Correct Answer
B. Apparent
Explanation
The longest side of the power triangle is the apparent power. Apparent power is the combination of real power (measured in watts) and reactive power (measured in vars). It represents the total power in an AC circuit, taking into account both the active and reactive components. The other options, such as watts, vars, reactive, and true, are all components of the power triangle but do not represent the longest side.
40.
A two winding transformer that has a lower primary voltage than its secondary is known as:
Correct Answer
C. A step up transformer
Explanation
A two winding transformer that has a lower primary voltage than its secondary is known as a step up transformer. This is because it steps up the voltage from the primary winding to the secondary winding.
41.
The RMS value of a sinusoidal wave is equal to the peak value times:
Correct Answer
D. .707
Explanation
The RMS value of a sinusoidal wave is equal to the peak value times 0.707. This is because the RMS value represents the effective value of the wave, which is equivalent to the value of a DC signal that would produce the same amount of power in a resistive load. For a sinusoidal wave, the peak value is the maximum value of the wave, and multiplying it by 0.707 gives the RMS value. This constant factor of 0.707 is derived from the mathematical relationship between the peak and RMS values of a sinusoidal wave.
42.
If the current lags the voltage by 90 degrees, it is purely a _____________ circuit.
Correct Answer
B. Inductive
Explanation
If the current lags the voltage by 90 degrees, it is purely an inductive circuit. This is because in an inductive circuit, the current lags behind the voltage due to the presence of inductance. Inductance causes the current to build up gradually, resulting in a phase shift between the voltage and current waveforms.
43.
A 119 volt, 60hz AC voltage is put across a series circuit with an 8 ohm resistor and a capacitor who's reactance is 15 ohms. What is the circuit impedance?
Z = Square root of (R^2 + Xc^2)
Correct Answer
B. 17 ohms
Explanation
The circuit impedance can be calculated using the formula Z = Square root of (R^2 + Xc^2), where R is the resistance and Xc is the reactance of the capacitor. In this case, the resistance is 8 ohms and the reactance is 15 ohms. Plugging these values into the formula, we get Z = Square root of (8^2 + 15^2) = Square root of (64 + 225) = Square root of 289 = 17 ohms. Therefore, the circuit impedance is 17 ohms.
44.
A 0.8 henry inductor is connected to a 120 volt, 60hz line. How much current will flow? hint: Z= (2xpi)(Frequency)(Henrys) and I= E/Z
Correct Answer
A. .398 amps
Explanation
The given question provides the value of inductance (0.8 henry) and the voltage (120 volts) of the circuit. It also mentions the frequency (60 Hz) and provides a hint to calculate the impedance (Z) using the formula Z = (2Ï€)(Frequency)(Henrys). Once the impedance is calculated, the formula I = E/Z can be used to determine the current. Therefore, the correct answer is .398 amps, which is the result of dividing the voltage (120 volts) by the impedance (calculated using the given formula).
45.
A 35 microfarad capacitor is connected to a 120 volt, 60 hz line. What is the value of Xc?
Correct Answer
C. 75.79π
Explanation
The value of Xc is determined by the formula Xc = 1 / (2πfC), where f is the frequency and C is the capacitance. In this case, the frequency is 60 Hz and the capacitance is 35 microfarads. Plugging these values into the formula, we get Xc = 1 / (2π * 60 * 35 * 10^-6) = 75.79π. Therefore, the value of Xc is 75.79π.
46.
In a series ac circuit that contains only capacative reactance and resistance, the current :
Correct Answer
D. Leads the voltage by less than 90 degrees
Explanation
In a series AC circuit that contains only capacitive reactance and resistance, the current leads the voltage by less than 90 degrees. This is because in a capacitive circuit, the current leads the voltage due to the fact that the capacitor charges and discharges ahead of the voltage. However, the presence of resistance in the circuit causes the current to be slightly delayed compared to a purely capacitive circuit, resulting in the current leading the voltage by less than 90 degrees.
47.
What is the kVA rating of a 3 phase generator rated at 100kW with a .9 power factor?
Correct Answer
A. 111 kVA
Explanation
The kVA rating of a generator is calculated by dividing the kW rating by the power factor. In this case, the generator is rated at 100 kW with a power factor of 0.9. Dividing 100 kW by 0.9 gives us a kVA rating of 111 kVA.
48.
What is the total circuit resistance?
Correct Answer
C. 20 ohms
Explanation
Based on the circuit diagram you sent, the total circuit resistance (RT) can be determined using the following formula for resistors in parallel:
1/RT = 1/R1 + 1/R2 + 1/R3
Where:
RT is the total resistance
R1, R2, and R3 are the values of the individual resistors
Plugging in the values from the image:
R1 = 50 ohms
R2 = 25 ohms
R3 = 25 ohms
1/RT = 1/50 + 1/25 + 1/25
1/RT = (1 + 2 + 2) / 100
1/RT = 5/100
RT = 100 / 5 ohms
RT = 20 ohms
Therefore, the total circuit resistance (RT) in the image is 20 ohms.
49.
What is the total power consumed in the circuit?
Correct Answer
E. 720 watts
Explanation
The total power consumed in the circuit is 720 watts. This can be calculated by adding up the power consumption of each component in the circuit.
50.
What current will flow in this circuit?
Correct Answer
A. 6 amps
Explanation
The current flowing in this circuit is 6 amps. This can be determined by applying Kirchhoff's current law, which states that the total current entering a junction is equal to the total current leaving the junction. Since there are no branches or junctions in the circuit, the current remains constant throughout. Therefore, the current flowing in the circuit is 6 amps.